1. Field
The present invention relates generally to wireless charging, and more specifically to devices, systems, and methods related to wireless power chargers.
2. Background
Typically, each battery-powered device such as a wireless communication device (e.g. a cell phone) requires its own charger and power source, which is usually the AC power outlet. This becomes unwieldy when many devices need charging, each requiring its own separate charger.
Approaches are being developed that use over-the-air or wireless power transmission between a transmitter and a receiver coupled to the electronic device to be charged. Such approaches generally fall into two categories. One is based on the coupling of plane wave radiation (also called far-field radiation) between a transmit antenna and a receive antenna on the device to be charged. The receive antenna collects the radiated power and rectifies the radiated power for charging the battery. Antennas are generally of resonant length in order to improve the coupling efficiency. This approach suffers from the fact that the power coupling falls off quickly with distance between the antennas, so charging over reasonable distances (e.g., less than 1 to 2 meters) becomes difficult. Additionally, because the transmitting system radiates plane waves, unintentional radiation may interfere with other systems if not properly controlled through filtering.
Other approaches to wireless energy transmission techniques are based on inductive coupling between a transmit antenna embedded, for example, in a “charging” device, mat, or surface and a receive antenna (plus a rectifying circuit) embedded in the host electronic device to be charged. This approach has the disadvantage that the spacing between transmit and receive antennas must be very close (e.g., within thousandths of meters). Though this approach does have the capability to simultaneously charge multiple devices in the same area, this area is typically very small and requires the user to accurately locate the devices to a specific area.
In addition to added convenience of simultaneous charging, environmental and cost concerns may also be addressed with wireless charging. Currently, many electronic devices are currently in use, which are powered by standard size batteries such as AA, AAA, D, C Cell, 9-Volt, etc., formats. These batteries may be primary cells or rechargeable, secondary cells. The primary cells are disposable and raise environmental issues. Rechargeable, secondary cells may help to address the environmental concern, but rechargeable, secondary cells may still require being removed from the device to be charged, which may include placing the rechargeable, secondary cells in a charger that may only have limit spaces for batteries, typically four batteries. With the advantages of wireless power charging, there may exist a need to convert (i.e., retrofit) existing devices which are powered by primary or secondary cells to be wireless be a wireless powered enabled device to recharge batteries or operate in a wireless charging field.